1. Field of Invention
The present invention relates to a stereoscopic display. More particularly, the present invention relates to a stereoscopic display having a gray level zone.
2. Description of Related Art
A conventional stereoscopic display (also 3D display) is implemented with a parallax barrier. Reference is made to FIG. 1A. FIG. 1A is a schematic diagram of the stereoscopic display 100 used in some approaches. As shown in FIG. 1A a 2D image is generated from a pixel layer 140, and the states of the parallax barrier cell 120 are changed to form a photic zone 102 or a shading zone 104. Thus, a better 3D image is provided to a user.
A liquid crystal (LC) barrier cell is commonly used to realize the parallax barrier cell. As shown in FIG. 1A, the parallax barrier cell 120 is twist nematic (TN) type liquid crystal barrier cell. By applying a driving voltage to the electrodes on opposite sides of the parallax barrier cell 120 (hereinafter referred to as “opposing electrodes”), shading zones 104 or photic zones 102 are able to be formed on the switchable barrier units 122. For illustration, if the parallax barrier cell 120 is a normally white LC, and a driving voltage is not applied to the opposing electrodes, the photic zones 102 are formed. Alternatively, if the driving voltage is applied to the opposing electrodes, the shading zones 104 are formed.
However, when the viewing position of the user changes (i.e., the positions of the user's eyes change), the positions of the photic zones 102 must be changed. That is, the driving voltages on each of the switchable barrier units 122 must be changed correspondingly, so as to allow the user to see a better 3D image. When the photic zones 102 and the shading zones 104 are switched (i.e., from the first mode to the second mode in FIG. 1A), the luminance of the image is changed, resulting in flickers on the screen.
FIG. 1B is a graph illustrating a relation curve of a visual angle and an average luminance. FIG. 1C is a schematic diagram of the luminance of the switchable barrier units being changed when the switchable barrier units are switched. There are two major reasons to make the luminance change. The first reason relates to the angular intensity being non-uniform. As shown in FIG. 1B, when the first mode is switched to the second mode, the switching operation is not able to be performed at a precise switching angle. Thus, the luminance of the first mode and the luminance of the second mode are different with respect to the same visual angle result in flickers on the screen. The second reason relates to the on-time and the off-time of the LC barrier cell being different. For example, as shown in FIG. 1C, when switching in two modes, the switchable barrier units 122 are able to be switched fast from the photic zones 102 to the shading zones 104. However, it takes a longer time for the switchable barrier units 122 to be switched from the shading zones 104 to the photic zones 102.
In addition, in FIG. 1A, a unity barrier pitch is set to include 8 groups of the switchable barrier units. In general, the greater the number of groups of the switchable barrier units, the smoother the switching of the image. However, due to the increasingly smaller pixel structure in modern high-resolution panels, the number of groups of the switchable barrier units is limited due to the manufacturing process. When the number of the groups of the switchable barrier units is insufficient, crosstalk increases, which results in a decrease in the smoothness of image switching.
Therefore, a heretofore-unaddressed need exists to address the aforementioned deficiencies and inadequacies.